What to Prioritise: Interoperability or Open Standards?

It is true that open standards compliance does not necessarily mean that compliant software applications are interoperable. But, open standards compliance makes the problem of broad interoperability tractable. It also removes the possibility of a supplier taking the role of gatekeeper, blocking would-be competitors.

If software conforms to an open standard, the gulf between any two compliant packages is tiny compared to that between any two products where there is no open standard. Also, focusing purely on interoperability without an open standard limits the interoperability to

two players who mutually agree to work together to negotiate interoperability, a process which excludes any parties not willing or able to collaborate, and

if there are, say, 5 competing products in a marketplace, full interoperability requires 52 = 25 collaborations and 25 different interoperability code-bases (which must also be maintained, coordinated and upgraded throughout the life cycle of each pair of software applications). That is absurdly inefficient and costly. Addressing that problem is why we have open standards in the first place.

If software must comply with an open standard, it means that it is possible for any motivated software supplier to achieve interoperability with the other software in the market without requiring the permission of any other suppliers, most of whom have a commercial incentive not to collaborate. While open standards compliance is not seen as desirable by most proprietary software suppliers (open source suppliers tend not to mind), compliance is always to the benefit of the market, who, in the case of government software procurement, are private industry and the general public: the taxpayer.